Conversion of hydrocarbon oils



I April 1942- F. w. LEFFE'R convsnsxou OF amocmaou' ons Filed Jan. 13, 1939 RECEIVER COOLER FRACTIONATOR RECEIVER VAPORIZINC & SEPARATINC CHAMBER CONDEN ER l3 5. J? at DISTILLINC COLUMN mm m FURNACE 42 'INVENTOR FRIEDRICH W. LEFFER I BY ATTORNEY Patented Apr. 28, 1942 CONVERSION OF HYDROCARBON OILS Friedrich W. Lefl'er, Kenton-Harrow, England, asslgnor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware Application January 13, 1939, Serial No. 250,772

8 Claims.

The invention particularly refers to an improved process for the distillation and pyrolytic conversion of hydrocarbon oils for the production therefrom of high yields of intermediate liquids, such as Diesel fuel and minor yields of lighter and heavier products, such as gasoline and heavy residual liquids.

More specifically, the invention is concerned with a process for the treatment of crude synthetic hydrocarbon liquids produced from the catalytic watergas reaction, such as the product derived from the Flscher-Tropsch synthesis, wherein materials boiling within the range of Diesel fuel may be separately recovered and blended with Diesel fuel produced by cracking to form a final blended product of the desired characteristics without subjecting the straight run product to conversion.- The product of the aforesaid Fischer-Tropsch synthesis is known in the art as Kogasin.

The invention is also concerned with a method and means of treating the components of said charging stock which boil intermediate the desired gasoline product and the Diesel fuel product, to produce additional gasoline of good antiknock properties.

Although the process of the invention is more particularly well adaptableto the treatment of crude synthetic hydrocarbon liquids of the class mentioned, it is also-adapted to the treatment of other hydrocarbon oils of a predominately aliphatic or parafilnic character and particularly to virgin oils containing materials which boil within the range of Diesel fuel and, in accordance with'the provisions of the invention, as stated above, are separately recovered without subjecting them to conversion.

I have found that the Diesel fuel fraction obtained by distillation of the liquid hydrocarbons produced in the catalytic water-gas synthesis has an excessively high octane number and usually also a high viscosity and is-therefore not desirable for direct use as a Diesel fuel. The cracked Diesel fuel, on the other hand, obtained by cracking the bottoms from the distillation of such an oil, has a lower cetane number and lower viscosity, and when blended with the product obtained by distillation, produces a Diesel fuel having the desired properties.

I have found that when cracking relatively high-boiling components of hydrocarbon oils, of

either natural or synthetic origin, for maximum yields of Diesel fuel, it is highly advantageous to use relatively mild cracking conditions which, in-this particular case, are obtained by employing relatively high cracking temperature and relatively short time at an active cracking tem-' fuel fractions and some lighter and heavier products, subjecting a part or all of said lower boiling components to more severe cracking or reforming treatment to produce therefrom high yields of gasoline of improved antiknock characteristics, cooling and commingling the products of both cracking operations, separating the commingled materials into residual liquid and vaporous products, removing the residual liquid from the system and fractionating the vapors to separate therefrom a heavy reflux condensate, returning the latter to the fi st mentioned cracking step, further fractionar'ng the remaining vapors to condense therefrom a cracked Diesel fuel, blending the latter with the Diesel fuel recovered in the fractional distilling step, removing fractionated vapors of the desired endboiling point from the last mentioned fractionating step and condensing the same to form good antiknock gasoline.

The accompanying drawing diagrammatically illustrates one specific form of apparatus embodying the features of the invention and in which the objects of the process may be accom- Plished.

Referring to the drawing, charging stock for the process, which may comprise any desired type of oil, but is preferably an aliphatic or parafiinic hydrocarbon oil of wide boiling range or a crude synthetic hydrocarbon oil of the type obtained from the catalytic watergas synthesis, may be supplied through line i and valve i to pump 3 by means of which it is fed through line 4 and valve 5 to heating coil I. Heat is imparted to the oil in passing through heating coil 6 from a suitable furnace I in which the heatfractionating column 19. Non-cracking conditions are preferably employed in coil 9.

The vaporous materials comprising the lower boiling components of the charge are fractionated in column I! to produce an overhead product comprising either materials boiling within the range of gasoline and gas or all of the components of the charging stock which boil below the desired Diesel fuel fraction. Preferably, however, distilling column I9 is operated with a top temperature controlled to give an overhead gasoline fraction of good antiknock properties. The overhead vaporous stream is directed from the upper portion of distilling column I I through line Ii of the desired end-boiling point, is withdrawn from receiver it through line II and valve 29 to storage or elsewhere as desired.

Any components of the charging stock which boil below the desired Diesel fuel and above the desired overhead distillate product are withdrawn from the upper portion of column 19 through line 23 and are directed through valve 24 to pump 29. When desired, and in the case where liquids recovered in receiver it are not suitable as a motor fuel, they may be withdrawn from receiver it through line 2| and valve 22 and directed to pump 25 through line 23 commingling therein with heavier fractions separately removed from column l9 through this line.

In either case, oil supplied to pump 29 is discharged therefrom through line 29 and may be directed through valve 26' in the same line to heating coil 40.

When desired, the materials contained in the fraction boiling intermediate to Diesel fuel and the overhead product may be subjected to polymerization and condensation with suitable agents, such as aluminum chloride, in aseparate polymerizing system of well known form, not illustrated, for the production of lubricating oils and the remaining non-polymerized constituents returned to the process and introduced to heating coil 49.

The components of the charge supplied to column l 0, which boil within the range of the desired Diesel fuel product, are withdrawn from a suitable intermediate point in the column through line 29 and valve 39 to stripping column 3| wherein they are subjected to reboiling to substantially free the same of any desirable lower boiling fractions and dissolved gases. This may be accomplished. for example, by passing a suitable heating medium, such as steam. hot oil, or-

the like, through coil 4i within the lower portion of column 3|. The evolved vapors and gases are returned from column 3! through line 92 and valve 33 to column Ill. The reboiled Diesel fuel is withdrawn from the lower portion of column 3| through line 94 and is directed through valve 35 to line 36 and thence to cooler 31. Diesel fuel produced by cracking, as subsequently described, is also supplied to cooler 91, blended and cooled Diesel fuel product being directed from cooler 31 through line 39 and valve 39 to storage or elsewhere as desired.

The oil supplied to heating coil 49, located in the fluid heating zone of furnace 42, receive heat 2,881,862 through line 8 and valve 9 into distilling and predominately by convection, are discharged therefrom through line 49 to heating coil 44 which is located in a radiant heating zone of the same furnace. The oil passing through heatin coil 44 is heated therein to a high cracking temperature at a substantial superatmospheric pressure and the heated products are discharged from coil 44 through line 49, valve 49, line 21 and line 41 into vaporizing and separating chamber 49.

The heavy components of the charge to column l9, which comprise materials boiling above desired Diesel fuel, are withdrawn from the lower portion thereof and directed through line 59 and valve ll to pump 52 by means of which they are fed through line 93 and valve 54 to heating coil 99.

The oil in passing through heating coil 95, which is disposed in furnace 42, is subjected therein to relatively mild cracking conditions and the resulting products are discharged therefrom through line 59, valve 51 and line 41 into chamber 49.

In order to definitely control the time during which the oil is maintained at an active crack-3 ing temperature and substantially limit such conversion to primary cracking reactions, the heated products which are discharged from heating coil 95 are preferably cooled sufficiently to prevent any substantial continued cracking in chamber 49. Since rapid cooling of the conversion products is desirable, the cooling is preferably accomplished by introducing cooling oil directly into line 41, although substantial pressure reduction and/or indirect heat exchange with any desired cooling material may replace or augment direct commingling of the conversion products with a cooling medium. Any desired oil, which will not cause restriction or plugging of transfer line 41 and will not contaminate the desired final product of the process, may be employed as a direct cooling medium. Regulated quantities of any of the products of the process other than the Diesel fuel may be employed as the cooling oil. An example of the use of such materials and means for supp ying the same to line 41 will be later more fully described. Preferably the products discharged from coil 44 are also cooled to below an active temperature before they are .introduced into chamber 49 and, preferably, before they. are commingled with the products from coil 55. Cooling of this stream from coil 44 may be accomplished in the same manner, above outlined, as the products from coil 59 are cooled and specific means of accomplishing this will be later described.

The conversion products supplied to chamber 49 are separated therein into vapors and residual liquid. The latter is directed from the lower portion of chamber 49 through line 59 and valve 59 to cooling and storage or elsewhere as desired. The vaporous products, comprising gas, gasoline, Diesel fuel and fractions heavier than the desired Diesel fuel which are suitable as stock for further cracking within the system are directed from the upper portion of chamber 49 to fractionator 62 through line 69 and valve 6|.

The relatively heavy reflux condensate formed by fractionation of the vaporous conversion products in fractionator 62 comprises substantially all of their components boiling above the desired Diesel fuel, and is removed from the lower portion of the fractionator through line 63 and valve 64 to pump 65 by means of which it is fed through line 66 and may, when desired, be directed all or in part through line 49 and valve 61 into line 41 as a cooling medium for the fractlonator 62.

menses hot conversion products with which itxis then commingled. Preferably, however, at least a portion of this oil is directed through valve II in line It and through line 58 to further cracking in coil with the bottoms from column II.

A selected lighter fraction of the reflux condensate formed in fractionator l! is removed as the desired cracked Diesel fuel from a suitable intermediate point in fractionator I! and is directed through line 09 and valve ll into stripping column ll wherein it is reboiled to substantially free the same of any undesired low-boiling fractions and dissolved gases. This reboiling is accomplished, in the case here illustrated, by passing a suitable heating medium, such as steam, hot oil or oil vapors or the like, through closed coil 12, disposed in the lower portion of column II. from column H through line 00 and valve 9| to The reboiled Diesel fuel is withdrawn from the lower portion of column H through line 36 and valve 02 to cooler 31 to commingle with the Diesel fuel recovered by distillation of the charging oil in column I! and form the final Diesel fuel product of the process.

It will, of course, be understood that stripping columns SI and H, although desirable, are not essential to the operation of the process and that, when desired, rebolling may be accomplished in any other well known manner, not illustrated, or may be dispensed with.

The components of the conversion products supplied to fractionator I! which boil within the range of the desired gasoline, are withdrawn from the upper portion of fractionator 62 and directed through line 80 and valve II to condenser I2. The resulting distillate and uncondensed gases are directed through line 82 and valve II to receiver 05. The uncondensed and undissolved gases are removed from the receiver through line 80 and valve II to storage or elsewhere as-desired. The distillate collected in receiver 85 is directed through line it and valve as to any desired further treatment or to storage or elsewhere as desired.

Any components of the vapors supplied to column 82 which boil below the desired Diesel fuel and above the desired gasoline are condensed as light reflux condensate in the upper portion of fractionator 62 and directed therefrom through line 13, valve H to pump II by means of which they are preferably fed, all or in part, through line 16, valve 11 and line I! to coils ll and 44 for further cracking. A portion or all of this material may be directed from line I. through line ll, valve It and lines TI and 41 into chamber I! to serve as a cooling medium for the con-, version products from coils 44 and I! by directly commingling therewith.

Regulated quantities of the light oil supplied to pump .25 in either or both of the manners previously described may likewise be employed, when desired, as a cooling medium for the conversion products in line 41 in which case they are directed from line 26 through line 21 and valve 28 into line 41.

Although not shown in the drawing. it is within the scope of the invention to employ stripping columns for obtaining more closely cut fractions when removing naphtha and/or heavy gasoline fractions from the distilling and fractionating steps in which case their operation would be similar to that given for columns ii and II. Regulated quantities of the distillate collected in receiver II and receiver I! may, when desired,

be returned to the upper portions of the respective columns II and I! to serve as cooling and refluxing liquid therein. I

The evolved gases and vapors are returned It will, of course, be understood that the various alternative methods of operation illustrated in the drawing are not equivalent but may be selectedto suit individual requirements, and that any of the methods illustrated in the drawing may be employed for cooling the conversion products prior to their introduction into the separating chamber, either alone or in conjunction with any other suitable method of cooling, such as, for example, indirect heat exchange between the hot conversion products and charging stock, or other cooling material.

. The preferred range of operating conditions which may be employed to accomplish the objects of the invention in an apparatus such as illustrated and above described is approximately as follows: I

The temperature at the outlet of the heating coil employed for heating the charge may range, for example, from 600 to 700 R, preferably with a relatively low pressure in the coil and fractionating column ranging, for example, from pounds or thereabouts per square inch, superatmospheric, down to substantially atmospheric pressure. Preferably substantially the same pressure is employed in both coil 8 and column it although lower pressure may be utilized in the distilling column, when desired. The temperature employed at the outlet of the heavy oil cracking coil may range, for example, from 850 to 1000 F. or thereabouts, preferably with a relatively low superatmospheric pressure in this zone ranging, for example, from 300 pounds or'thereabouts per square inch down to substantially atmospheric pressure and with a reaction time substantially less than seconds and preferably less than 30 seconds based on the cold oil velocity. The heating coil to which the naphtha and/or low antiknock gasoline fractions are supplied may employ an outlet temperature of from 900 to 1050 F., or more, with a superatmospheric pressure ranging, for example, from 300 to 1200 pounds or more per square inch. Vaporizing and separating chamber 49 is preferably operated under temperature and pressure conditions which -wi1l not permit any substantial further cracking of the products supplied thereto. The pressure may be substantially reduced in this zone relative to that employed in coil 44 and/or coil 45, said reduced pressure ranging, for example, from substantially atmospheric to 60 pounds or thereabouts per square inch superatmospheric. The temperature employed in chamber 4! may range, for example, from 650 to 790 F. or thereabouts. The pressure employed in chamber 0 may be substantially equalized or reduced in the succeeding fractionating, condensing and collecting portions of the system.

As a specific example of an operation oi the process, as it may be conducted in an apparatus, such as illustrated and above described. the charging stock comprising a wide boiling range synthetic hydrocarbon liquid produced in the Fischer-Tropsch synthesis is quickly heated in coil 8 to a temperature of about 650 1''. at a superatmospheric pressure of about 30 pounds per square inch and thence introduced into the distilling column wherein it is separated at substantially atmospheric pressure into the desired components. The low-boiling components of the charge having an end-boiling point of about 250 F. are withdrawn from the upper portion of the distilling column in vaporous state and subjected to condensation and collection for the recovery of a gasoline product of satisfactory antiknock value. Heavier gasoline and naphtha fractions having a boiling range of about 240 to 410 F. are withdrawn as light condensate from the upper portion of the distilling column and subjected to reforming treatment in coil 44, in admixture with recycle stock from fractionator 62. A conversion temperature of approximately 1040 F. and a superatmospheric pressure of about 750 pounds per square inch are employed at the outlet of coil 44. The highly heated reformed products are cooled to a temperature of approximately 750 F. by direct contact with the heavy reflux condensate produced, as hereinafter described, in the fractionator of the cracking system after which they are introduced into a vaporizing and separating chamber. The Diesel fuel fraction recovered from column ID has a boiling range of about 400 to 650 F. The heavy bottoms from the distilling column, comprising the components of the charge boiling above approximately 650 F. are subjected to conversion in coil 55 at a temperature of approximately 950 F. and a superatmospherlc pressure of approximately 60 pounds per square inch, the conversion time in coil 55 being approximately 30 seconds based on the cold oil velocity. The resulting hot conversion products are quickly cooled to a temperature of about 750 F. along with the conversion products obtained from the reforming coil, as hereinbefore described, whereupon they are introduced into the vaporizing and separating chamber which is operated at a pressure of approximately 60 pounds per square inch. The vaporous conversion prodnets are separated from the residual liquid conversion products in chamber 49 and the latter are withdrawn from the chamber, cooled and recovered as a product of the process. The vaporous conversion products are subjected to fractionation for the production of heavy reflux condensate, gasoline, and the desired intermediate products comprising naphtha and cracked Diesel fuel. Vapors boiling up to approximately 380 F. are withdrawn from the upper portion of fractlonator 62, subjected to condensation and the resulting good antiknock gasoline recovered. Naphtha fractions boiling within the range of from approximately 380 to 455 F. are withdrawn as a side stream from fractionator 62 and commingled as previously described, with the heavy gasoline and naphtha supplied to coils l and 44 from fractionator Ill. Cracked Diesel fuel, comprising the components of th vapors supplied to fractionator 62, which boil within the range of about 455 F. to 650 F., is withdrawn from an intermediate point in fractionator 62,

1 commingled with a Diesel fuel obtained from the fractional distilling step and commingled materials are'cooled and recovered as the final Diesel fuel product. The heavy reflux condensate, formed in fractionator 62 is recycled, as previously described, to furnish the necessary cooling to the conversion products prior to their introduction into the vaporizing and separating chamber. This operation will produce, per barrel of charging stock, approximately 31% of good quality Diesel fuel, including the cracked and straightrun product, approximately 57% good antiknock gasoline, and about 1% of good quality residual oil, the remainder being chargeable principally to uncondensible gas and loss.

I claim as my invention: 1. The process of t eating a synthet c hydro- 75 carbon oil resulting from the interaction of carbon monoxide and hydrogen, which comprises separating from said 011 by fractional distillation thereof, without appreciable cracking, a Dieselfuel of unusually high cetene number, selected lower boiling fractions and fractions boiling above the range of said Diesel fuel, cracking said lower boiling fraction under conditions regulated to produce therefrom high yields of good antiknock gasoline, separately cracking said higher boiling fractions under conditions regulated to produce therefrom high yields of cracked Diesel fuel, commingling the products of both cracking operations and cooling the same to below an active cracking temperature, separating the resulting cooled and commingled products into vapors and non-vaporous residue, fractionating the vapors to form condensate consisting of cracked Diesel fuel having a low cetene number and an overhead vaporous stream comprising materials of good antiknock value boiling within the range of gasoline, condensing said overhead vaporous stream, recovering the resulting distillate, and blending Diesel fuels resulting from said distilling and cracking steps to form a final Diesel fuel product of the desired characteristics.

2. The process defined in claim 1, wherein a condensate heavier than said cracked Diesel fuel is condensed from the vapors in the second mentioned fractionating step, separately removed therefrom and returned to the second mentioned cracking step for further cracking treatincnt.

3. The process defined in claim 1, wherein a condensate heavier than said cracked Diesel fuel is condensed from the vapors in the second mentioned fractionating step, separately removed therefrom and wherein regulated quantities of said higher boiling condensate are directly commingled with said conversion products to effect at least a portion of said cooling of the latter.

4. The process defined in claim 1, wherein selected fractions of the charging stock, boiling below said high cetene number Diesel fuel, are removed from the distilling step and directly commingled with said conversion products to effect at least a portion of said cooling of the latter.

5. The process defined in claim 1, wherein selected fractions of the vaporous conversion products, boiling intermediate said cracked gasoline and said cracked Diesel fuel, are separately removed as light reflux condensate from the last mentioned fractionating step and directly commingled with said conversion products to effect at least a portion of said cooling of the latter.

6. The process defined in claim 1, wherein selected fractions of the charging stock and selected fractions of the vaporous conversion products, boiling below the Diesel fuels formed in the respective fractionating steps, are removed therefrom and directly commingled with said conversion products to effect at least a portion of said cooling of the latter.

"I. The process defined in claim 1, wherein selected fractions of the charging stock and selected fractions of the vaporous conversion products, boiling below the Diesel fuels formed in the respective fractionating steps, are removed therefrom, a regulated portion thereof being commingled with said conversion products to effect at least a portion of said cooling of the latter and another regulated portion thereof being supplied to the first mentioned cracking oper. ation.

8. A process for producing Diesel fuel from Kogasin which comprises iractionaiiy distilling such as to convert the same predominantly into lighter hydrocarbons boiling in the Diesel fuel range, iractionating the resultant conversion products to separate a cracked Diesel fuel therefrom, and blending the latter with said firstmentioned fractions to form a Diesel fuel product oi satisfactory cetene number and viscosity.

FRIEDRICH W. LEF'FERQ 

